1. Technical Field
The present invention relates to an apparatus and method for inspecting defects in a circuit pattern.
2. Description of the Related Art
Recently, with the development of computer and communication technology, the transfer speed of signals in electronic devices has become an important parameter. Accordingly, decreasing impedance between parts and wires in a Printed Circuit Board (PCB) and matching the impedance therebetween have become very important. In order to realize low impedance, a PCB is designed such that fine wiring patterns are formed and wiring density is also increased.
Meanwhile, as wiring patterns on a PCB become fine, the open and short circuits of the wiring patterns may cause problems. Further, in order to check the reliability of wiring patterns formed on a PCB, whether wiring patterns have open- or short-circuited is tested.
As a demand for PCBs has increased, testing for wiring patterns on PCBs also requires high precision, high speed and low cost so that a large number of PCBs can be precisely and promptly tested. Meanwhile, although a requirement for high-reliability and high-speed measurement has increased, an effective method meeting such a requirement has not yet been proposed, and thus a method using probes is currently being used.
FIG. 1 is a sectional view showing a conventional apparatus for inspecting defects in a circuit pattern using contact probes. Hereinafter, a conventional apparatus and method for inspecting defects in a circuit pattern will be described with reference to FIG. 1.
The conventional apparatus for inspecting defects in a circuit pattern includes two pin probes 1 and 2, a voltage source 3 and an ammeter 4.
The first pin probe 1 is installed to come into contact with the circuit pattern 6 of a substrate 5, which is a target to be inspected, and is configured to input a voltage received from the voltage source 3 to the inspection target circuit pattern 6. Therefore, a conical portion of the first pin probe 1 is connected to the inspection target circuit pattern 6, and the portion of the first pin probe 1 which is opposite the conical portion is connected to the voltage source 3 through the lead wire of the first pin probe 1.
The second pin probe 2 is installed to come into contact with a connection circuit pattern 7, of which the electrical connection with the inspection target circuit pattern 6 is desired to be examined. Therefore, a conical portion of the second pin probe 2 is connected to the connection circuit pattern 7, and the portion of the second pin probe 2 which is opposite the conical portion is connected to the lead wire of the second pin probe 2.
The ammeter 4 is a component for measuring current flowing through a closed circuit, and is installed in series with lead wires connected to the first pin probe 1 and the second pin probe 2.
A conventional method of inspecting defects in a circuit pattern is described below.
When the inspection target circuit pattern 6 is normally connected to the connection circuit pattern 7, current flows from the voltage source 3 sequentially through the first pin probe 1, the inspection target circuit pattern 6, the connection circuit pattern 7, and the second pin probe 2. The current is measured by the ammeter 4, and the entire resistance can be measured by applying the current to the formula of Ohm's law, that is, R=V/I. Theoretically, when the inspection target circuit pattern 6 is normally connected to the connection circuit pattern 7, the resistance must be ‘0’. However, since there are resistances of the lead wires and the pin probes 1 and 2 themselves, the entire resistance is not ‘0’ and is derived as a relatively small value.
In contrast, when the inspection target circuit pattern 6 is not normally connected to the connection circuit pattern 7, current does not flow through a closed circuit, and the resistance becomes infinite.
Accordingly, the above resistances are compared with each other, and thus whether defects are present in the circuit pattern can be examined.
However, as described above, in the case when the contact pin probes 1 and 2 are used both in the inspection target circuit pattern 6 and in the connection circuit pattern 7, even if the circuit patterns are not normally connected, the circuit patterns may be measured as if they were normally connected to each other due to the contact pressure of the pin probes 1 and 2. That is, there is a problem in that the occurrence of erroneous measurements may increase.
Further, there is a problem in that the pin probes 1 and 2 come into contact with all unit circuit patterns, thus increasing the time required for measurements.